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author Rob Landley <rob@landley.net>
date Thu, 31 Jan 2013 04:05:56 -0600
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<title>Toybox Roadmap</title>

<h2>Goals and use cases</h2>

<p>We have several potential use cases for a new set of command line
utilities, and are using those to determine which commands to implement
for Toybox's 1.0 release.</p>

<p>Our current candidate list combines the commands toybox already implements,
the development environment command list, the toolbox standard commands,
various vendor configurations of busybox, a selected subset of the POSIX/SUSv4
standard, a couple of the less-insane bits of LSB, a few outright requests,
plus additional to-be-determined shell functionality.</p>

<p>See the <a href=status.html>status page</a> for the combined list
and progress towards implementing it.</p>

<hr />
<a name="standards">
<h2>Use case: standards compliance.</h2>

<h3><a name=susv4 /><a href="#susv4">POSIX-2008/SUSv4</a></h3>
<p>The best standards are the kind that describe reality, rather than
attempting to impose a new one.  (I.E. a good standard should document, not
legislate.)</p>

<p>The kind of standards which describe existing reality tend to be approved by
more than one standards body, such ANSI and ISO both approving C.  That's why
the IEEE POSIX committee's 2008 standard, the Single Unix Specification version
4, and the Open Group Base Specification edition 7 are all the same standard
from three sources.</p>

<p>The <a href="http://pubs.opengroup.org/onlinepubs/9699919799/idx/utilities.html">"utilities"
section</a>
of these standards is devoted to the unix command line, and are the best such
standard for our purposes.  (My earlier work on BusyBox was implemented with
regard to SUSv3, an earlier version of this standard.)</p>

<h3>Problems with the standard</h3>

<p>Unfortunately, these standards describe a subset of reality, lacking any
mention of commands such as init, login, or mount required to actually boot a
system. It provides ipcrm and ipcs, but not ipcmk, so you can use System V IPC
resources but not create them.</p>

<p>These standards also contain a large number of commands that are
inappropriate for toybox to implement in its 1.0 release.  (Perhaps some of
these could be reintroduced in later releases, but not now.)</p>

<p>Starting with the full "utilities" list, we first remove generally obsolete
commands (compess ed ex pr uncompress uccp uustat uux), commands for the
pre-CVS "SCCS" source control system (admin delta get prs rmdel sact sccs unget
val what), fortran support (asa fort77), and batch processing support (batch
qalter qdel qhold qmove qmsg qrerun qrls qselect qsig qstat qsub).</p>

<p>Some commands are for a compiler toolchain (ar c99 cflow ctags cxref gencat
iconv lex m4 make nm strings strip tsort yacc), which is outside of toybox's
mandate and should be supplied externally.  (Again, some of these may be
revisited later, but not for toybox 1.0.)</p>

<p>Some commands are part of a command shell, and cannot be implemented as
separate executables (alias bg cd command fc fg getopts hash jobs kill read
type ulimit umask unalias wait).  These may be revisited as part of a built-in
toybox shell, but are not exported into $PATH via symlinks.  (If you fork a
child process and have it "cd" then exit, you've accomplished nothing.)</p>

<p>A few other commands are judgement calls, providing command-line
internationalization support (iconv locale localedef), System V inter-process
communication (ipcrm ipcs), and cross-tty communication from the minicomputer
days (talk mesg write).  The "pax" utility was supplanted by tar, "mailx" is
a command line email client, and "lp" submits files for printing to... what
exactly?  (cups?)  The standard defines crontab but not crond.</p>

<p>Removing all of that leaves the following commands, which toybox should
implement:</p>

<blockquote><b>
<span id=posix>
at awk basename bc cal cat chgrp chmod chown cksum cmp comm cp
csplit cut date dd df diff dirname du echo env expand expr false file find
fold fuser getconf grep head id join kill link ln logger logname ls man
mkdir mkfifo more mv newgrp nice nl nohup od paste patch pathchk printf ps
pwd renice rm rmdir sed sh sleep sort split stty tabs tail tee test time
touch tput tr true tty uname unexpand uniq unlink uudecode uuencode vi wc
who xargs zcat
</span>
</b></blockquote>

<h3><a name=sigh /><a href="#sigh">Linux Standard Base</a></h3>

<p>One attempt to supplement POSIX towards an actual usable system was the
Linux Standard Base. Unfortunately, the quality of this "standard" is
fairly low.</p>

<p>POSIX allowed its standards process to be compromised
by leaving things out, thus allowing IBM mainframes and Windows NT to drive
a truck through the holes and declare themselves compilant. But it means what
they DID standardize tends to be respected.</p>

<p>The Linux Standard Base's failure mode is different, they respond to
pressure by including special-case crap, such as allowing Red Hat to shoehorn
RPM on the standard even though all sorts of distros (Debian, Slackware, Arch,
Gentoo) don't use it and probably never will. This means anything in the LSB is
at best a suggestion: arbitrary portions of this standard are widely
ignored.</p>

<p>The LSB does specify a <a href=http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/cmdbehav.html>list of command line
utilities</a>:</p>

<blockquote><b>
ar at awk batch bc chfn chsh col cpio crontab df dmesg du echo egrep 
fgrep file fuser gettext grep groupadd groupdel groupmod groups 
gunzip gzip hostname install install_initd ipcrm ipcs killall lpr ls 
lsb_release m4 md5sum mknod mktemp more mount msgfmt newgrp od passwd 
patch pidof remove_initd renice sed sendmail seq sh shutdown su sync 
tar umount useradd userdel usermod xargs zcat
</b></blockquote>

<p>Where posix specifies one of those commands, LSB's deltas tend to be
accomodations for broken tool versions which aren't up to date with the
standard yet. (See <a href=http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/more.html>more</a> and <a href=http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/xargs.html>xargs</a>
for examples.)</p>

<p>Since we've already committed to using our own judgement to skip bits of
POSIX, and LSB's "judgement" in this regard is purely bug workarounds to declare
various legacy tool implementations "compliant", this means we're mostly
interested in the set of tools that aren't specified in posix at all.</p>

<p>Of these, gettext and msgfmt are internationalization, install_initd and
remove_initd aren't present on ubuntu 10.04, lpr is out of scope, and
lsb_release is a distro issue (it's a nice command, but the output of
lsb_release -a is the name and version number of the linux distro you're
running, which toybox doesn't know).</p>

<p>This leaves:</p>

<blockquote><b>
<span id=lsb>
chfn chsh dmesg egrep fgrep groupadd groupdel groupmod groups
gunzip gzip hostname install killall md5sum
mknod mktemp mount passwd pidof sendmail seq shutdown
su sync tar umount useradd userdel usermod zcat
</span>
</b></blockquote>

<hr />
<a name="dev_env">
<h2><a href="#dev_env">Use case: provide a self-hosting development environment</a></h2>

<p>The following commands are enough to build the Aboriginal Linux development
environment, boot it to a shell prompt, and build Linux From Scratch 6.8 under
it. (Aboriginal Linux currently uses BusyBox for this, thus provides a
drop-in test environment for toybox. We install both implementations side
by side, redirecting the symlinks a command at a time until the older
package is no longer used, and can be removed.)</p>

<p>This use case includes running init scripts and other shell scripts, running
configure, make, and install in each package, and providing basic command line
facilities such as a text editor. (It does not include a compiler toolchain or
C library, those are outside the scope of this project.)</p>

<blockquote><b>
<span id=development>
bzcat cat cp dirname echo env patch rmdir sha1sum sleep sort sync
true uname wc which yes zcat
awk basename bzip2 chmod chown cmp cut date dd diff
egrep expr find grep gzip head hostname id install ln ls
mkdir mktemp mv od readlink rm sed sh tail tar touch tr uniq
wget whoami xargs chgrp comm gunzip less logname man split
tee test time bunzip2 chgrp chroot comm cpio dmesg
dnsdomainname ftpd ftpget ftpput gunzip ifconfig init less
logname losetup man mdev mount mountpoint nc pgrep pkill 
pwd route split stat switch_root tac umount vi
</span>
</b></blockquote>

<p>Note: Aboriginal Linux installs bash 2.05b as #!/bin/sh and its scripts
require bash extensions not present in shells such as busybox ash.
This means that toysh needs to supply several bash extensions _and_ work
when called under the name "bash".</p>

<hr />
<h2><a name=android /><a href="#android">Use case: Replacing Android Toolbox</a></h2>

<p>Android has a policy against GPL in userspace, so even though BusyBox
predates Android by many years, they couldn't use it. Instead they grabbed
an old version of ash and implemented their own command line utility set
called "toolbox".</p>

<p>Toolbox doesn't have its own repository, instead it's part of Android's
<a href=https://android.googlesource.com/platform/system/core>system/core
git repository</a> (this analysis looked at commit 51ccef27cab58).</p>

<h3>Toolbox commands:</h3>

<p>According to core/toolbox/Android.mk the toolbox directory builds the
following commands:</p>

<blockquote><b>
ls mount cat ps kill ln insmod rmmod lsmod ifconfig setconsole
rm mkdir rmdir reboot getevent sendevent date wipe sync umount
start stop notify cmp dmesg route hd dd df getprop setprop watchprops
log sleep renice printenv smd chmod chown newfs_msdos netstat ioctl 
mv schedtop top iftop id uptime vmstat nandread ionice touch lsof md5 r
</b></blockquote>

<p>If selinux is enabled, you also get:</p>
<blockquote><b>
getenforce setenforce chcon restorecon runcon getsebool setsebool load_policy
</b></blockquote>

<p>The Android.mk file also refers to dynarray.c and toolbox.c as library
code. This leaves the following apparently unused C files in toolbox/*.c, each
of which has a command_main() function and seems to implement a standalone
command:</p>

<blockquote><b>
alarm exists lsusb readtty rotatefb setkey syren
</b></blockquote>

<h3>Command shell (ash)</h3>

<p>The core/sh subdirectory contains a fork of ash 1.17, and sucks in
liblinenoise to provide command line history/editing.</p>

<h3>Other Android core commands</h3>

<p>Other than the toolbox and sh directories, the currently interesting
subdirectories in the core repository are fs_mgr, gpttool, init,
logcat, logwrapper, mkbootimg, netcfg, run-as, and sdcard.</p>

<ul>
<li><b>fs_mgr</b> - subset of mount</li>
<li><b>gpttool</b> - subset of fdisk</li>
<li><b>init</b> - Android's PID 1</li>
<li><b>logcat</b> - read android log format</li>
<li><b>logwrapper</b> - redirect stdio to android log</li>
<li><b>mkbootimg</b> - create signed boot image</li>
<li><b>netcfg</b> - network configuration (sucks in libnetutils)</li>
<li><b>run-as</b> - subset of sudo</li>
<li><b>sdcard</b> - FUSE wrapper to squash UID/GID/permissions to what FAT supports.</li>
</ul>

<p>Almost all of these reinvent an existing wheel with less functionality and a
different user interface. We may want to provide that interface, but
implementing the full commands (mount, fdisk, init, ifconfig with dhcp,
and sudo) come first.</p>

<p>Although logcat/logwrapper also reinvent a wheel, Android did so in the
kernel and these provide an interface to that.</p>

<p>Also, gpttool and mkbootimg are install tools, and sdcard looks like a
testing tool. These aren't a priority if android wants to use its own
bespoke code to install itself.</p>

<h3>Analysis</h3>

<p>For reference, combining everything listed above, we get:</p>

<blockquote><b>
alarm ash cat chcon chmod chown cmp date dd df dmesg exists fs_mgr getenforce
getevent getprop getsebool gpttool hd id ifconfig iftop init insmod ioctl
ionice kill ln load_policy log logcat logwrapper ls lsmod lsof lsusb md5
mkbootimg mkdir mount mv nandread netcfg netstat newfs_msdos notify printenv
ps r readtty reboot renice restorecon rm rmdir rmmod rotatefb route run-as
runcon schedtop sdcard sendevent setconsole setenforce setkey setprop setsebool
sleep smd start stop sync syren top touch umount uptime vmstat watchprops wipe
</b></blockquote>

<p>We may eventually implement all of that, but for toybox 1.0 we need to
focus a bit. For our first pass, let's ignore selinux, strip out the "unlisted"
commands except lsusb, and grab just logcat and logwrapper from the "core"
commands (since the rest have some full/standard version providing that
functionality, which we can implement a shim interface for later).</p>

<p>This means toybox should implement:</p>
<blockquote><b>
<span id=toolbox>
cat chmod chown cmp date dd df dmesg getevent getprop hd id ifconfig iftop
insmod ioctl ionice kill ln log logcat logwrapper ls lsmod lsof lsusb md5 mkdir
mount mv nandread
netstat newfs_msdos notify printenv ps r reboot renice rm rmdir rmmod route
schedtop sendevent setconsole setprop sleep smd start stop sync top touch
umount uptime vmstat watchprops wipe
</span>
</b></blockquote>

<p>The following Toolbox commands are already covered in previous
sections of this analysis:</p>

<blockquote><b>
cat chmod chown cmp date dd df dmesg id ifconfig insmod kill ln ls lsmod
mkdir mount mv ps renice rm rmdir rmmod route sleep sync top touch umount
</b></blockquote>

<p>Which leaves the following commands as new from Toolbox:</p>

<blockquote><b>
getevent getprop hd iftop ioctl ionice log lsof nandread netstat
newfs_msdos notify printenv r reboot schedtop sendevent setconsole
setprop smd start stop top uptime vmstat watchprops wipe
</b></blockquote>

<hr />
<h2>Requests:</h2>

<p>The following additional commands have been requested by various users:</p>
<blockquote><b>
<span id=request>
freeramdisk getty halt hexdump hwclock klogd modprobe ping ping6 pivot_root
poweroff rev sfdisk sudo syslogd taskset telnet telnetd tracepath traceroute
unzip usleep vconfig zip free login modinfo unshare netcat help w
</span>
</b></blockquote>

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